LONDON, England --Sunscreen creams may be less effective than previously thought in blocking the harmful rays that can cause skin cancer, according to research.

Scientists from the medical research charity the Restoration of Appearance and Function Trust (RAFT), based at Mount Vernon Hospital in north London, have found that even when the creams are applied in the correct dosage, harmful ultraviolet A (UVA) light is still able to penetrate to the skin beneath.

UVA rays can cause the skin cancer melanoma, as well as premature aging. Almost 1,500 people die in the UK each year from malignant melanoma.

According to RAFT sunscreen lotions may actually increase the risk of melanoma by giving people a false sense of security about being in the sun.

"Since the use of sunscreen creams encourages people to stay longer in the sun and the protection afforded by these creams against UVB far outweighs that against UVA - the use of sunscreen creams may therefore indirectly increase the risk of developing the skin malignancy melanoma," a RAFT spokeswoman told the Press Association (PA).

The RAFT research involved taking skin from patients who had undergone surgery and exposing it to UVA light at intensities similar to that of sunlight.

Three popular sun protection creams, which stated they contained some UVA protection, were applied to the skin in recommended doses. The research showed that the creams did not offer sufficient protection against the release of free radicals, the harmful molecules that can destroy cells and precipitate cancer.

The findings have confirmed warnings from Cancer Research UK that while sunscreen can protect against ultraviolet B (UVB) light, it is less effective against UVA rays.

"The way sun creams are tested today is really inadequate because they just show how much protection there is against UVB," Dr. Mark Birch-Machin, skin cancer expert at Cancer Research UK, told PA.

"The maximum UVA protection according to the current star system is four stars, but even at four stars, the amount of UVA protection is only 80% as good as the UVB protection."

Sunscreen manufacturers, however, have insisted that their products do offer good protection.

"You shouldn't assume that just because you're wearing sunscreen you're completely protected," a spokeswoman for Boots, a high-street chemist that produces its own range of sun lotions, told PA.

"However, wearing sunscreen and being sensible in the sun is far better than the alternatives, and we think it's unrealistic to ask people to stay out of the sun."

RAFT now wants to collaborate with sunscreen manufacturers to test and develop more effective sun creams.

In the meantime it is advising holiday makers to be aware that sunscreens do not necessarily offer full protection against the harmful effects of the sun.

"By all means use the creams to protect against skin damage from UVB rays," says RAFT researcher Dr. Claire Linge. "Don't use them, however, to prolong your sunbathing."